The present invention relates to an automobile brake shoe assembly. In particular, the invention relates to a brake shoe assembly which is fashioned so as to reduce vibratory noise caused upon application of the brake shoe against the brake drum in a moving vehicle.
In general, brake shoes comprise an arcuate supporting table having a conforming brake lining fastened thereto by rivets. The table is generally formed with a smooth concave upper surface, so that the smooth bottom concave surface of the lining can be tightly fastened thereon, and can fully contact the entire surface of the brake shoe table.
Despite the widespread use of this typical brake shoe, there is a serious and chronic drawback resulting from the unpleasant noise arising when the brake is actuated. This noise results directly from the frictional contact between the brake shoe and the brake drum. However, the basic cause of the noise is a vibratory sound phenomenon known as "squeal". This phenomenon occurs as the brakes are actuated at a certain speed and pressure. The excitation caused by the frictional contact between the brake shoe and the brake drum results in each of the elements vibrating at a certain natural frequency, dependent upon the speed and pressure, and materials used. When the frequencies of the brake shoe and the brake drum are coincidental, resonance occurs and the noise level becomes amplified resulting in squeal. Often, the resulting squeal is so loud as to cause extreme aural discomfort to those in and around the vehicle.
It is therefore an object of the present invention to provide a brake shoe which is capable of reducing or eliminating squeal, regardless of the vehicle speed or actuation pressure of the brake assembly.
It is a further object of the present invention to provide a brake shoe having an excitation frequency which is out of the range of the excitation frequency of the brake drum so as to prevent resonance.